You need a guide - literally, someone who will listen to you and guide you towards a more "native" pronunciation. Some italki members have recorded themselves online and posted a link here for feedback. You could use vocaroo.com - you record directly to the website, and there's no need to make an account.
Basically, you need to identify the habits from your first language that you are imposing onto your English speech, and change these old habits for new ones.
Hi. I just read what you wrote. Anyway, you should have said: I would like to lose my Brazilian accent, not "lost". After some time you will have lost your accent. Some of my students are Brazilian. I really like Brazilians. Anyway, I've noticed that a lot of Brazilians have a problem saying a verb in past tense. This is difficult for anyone, though, because the ed (for example - jumped) looks like you should say jum ped. But, it has to be pronounced like jumpt. In some past tense verbs, though, you should pronounce the ed as ED. It takes a lot of practice to know which verbs to use with which sounds. Also, it seems that Brazilians sometimes put the sound of ee at the end of a word. I'm not sure why this happens. Also, as I'm sure you know, R needs to sound like R, and not H.
You will reduce your Brazilian accent over time. There's nothing wrong with keeping a bit of Brazilian accent, though. It can become part of our identity, I think to have the accent of our home country. I know someone in my town that is from Australia and has lived here for 25 years. He still has a bit of his Australian accent. It makes him special and unique. So, don't worry too much about your accent. The important thing is that people who speak English understand you easily enough.
With respect: One has to ask why do you want to lose your accent? Accents are wonderful things. The important part of speaking a second language is to be understood. If you find people cannot understand you, then it's pronunciation you need to work on.
To understand the features of pronunciation: abc/letter sounds, word stress, sentence stress, intonation (ie. the rise & fall of the language), the linking of sounds, rhythm etc. there's a really nice activity you can do called sound scripting. Basically, record a few sentences from an English audio website/program you like, write it on paper yourself and then.
1. mark the pauses with a slash /
2. mark the stressed words in the sentence (these are usually the nouns and/or words that carry the main content of the message)
Once you have understood how to do this, you will notice other things going on with the language.
Also, the 'BBC Learning English' website page has a useful self-teaching section on pronunciation.
I hope this helps.